DNA damage induced by hydroquinone and catechol was detected by an electrochemical method. Calf thymus DNA was immobilized onto the surface of a pretreated glassy carbon electrode (GCE(ox)) to form a DNA/GCE(ox) modified electrode. Then the DNA/GCE(ox) was incubated in acetate buffer solution containing hydroquinone or catechol at a constant potential for the desired time. Differential pulse voltammetric experiments were then performed. The anodic peaks corresponding to the oxidation of guanisine and adenosine on the electrode could be observed on voltammetric curves. The experimental results showed that DNA damage could be detected using electrochemical DNA biosensors. The extent of DNA damage could be electrochemically recognized via the change of the anodic peak current. DNA damage induced by hydroquinone was greater than that by catechol. The response conditions were optimized with respect to DNA concentration, pH, ionic strength, and other variables.